It's not the most anatomically correct triceratops, but it is the first piece of origami that I've designed myself, rather than folding from someone else's diagram. You should be able to fold on yourself, from this hastily drawn crease pattern.
As you can plainly see, the corner flaps are the legs, while the central flaps form the frill at the top, head at the bottom, and horns on each side... OK unless you're an origami junkie yourself, you probably can't tell what that mess is, so I've made some handy folding diagrams too.
It starts with the traditional frog base, so if you know that one, you're half way there already.
Have fun folding.